I. Field of the Invention:
This invention relates generally video display apparatus, and more particularly to a video receiver and display system whereby the image created on the face of the cathode ray tube is perceived in three-dimensional form by the viewer.
II. Discussion of the Prior Art:
It has long been the desire in the television and computer display terminal industries to provide a 3-D presentation of images presented on the face of a cathode ray tube. Up until now, systems designed to accomplish this end have suffered from various drawbacks inherent in the particular scheme employed.
The principle of three-dimensional viewing is based upon the ability of the viewer's eyes to determine the relative depth of the object in view. This "depth perception" is created when the viewer's eyes observe an object from slightly different angles.
It is known in the art that stereographic display can be created by providing video information of a scene to the eyes as they would normally view that scene, but providing different views of the same scene to each eye. That is to say, the views of the same scene are taken from two angles that resemble the viewing angles of a person's two eyes. These two video scenes are then provided to the viewer via a cathode ray tube, typically with the aid of an electromechanical shutter device which rapidly switches back and forth to allow the viewer to focus on the face of the CRT screen as it directs alternate video frames to each eye.
For example, as set out in the May 1989 issue of Lasers & Optics, at page 45, the Tektronix Corporation of Beaverton, Oreg., employs a liquid crystal screen in front of the CRT face and means are provided for rapidly switching the liquid crystals much like a shutter, such that the display is alternately created for the right eye and left eye. The viewer then wears a set of polarized glasses where the lens associated with one eye is circularly polarized in a first direction and that with the other eye is circularly polarized in the opposite direction. The liquid crystal device when switched one way, polarizes all of the light in a first direction and, when electronically switched, then polarizes the light in the opposite direction. Hence, when viewed through differently polarized lenses, the left eye sees one scene at one time and the right eye subsequently sees substantially the same scene, but from a different angle, at a slightly later time The switching occurs so rapidly that it is effectively flicker-free.
Not only must the viewer wear special glasses to receive a 3-D image from the Tektronix scheme, but that device allows only half of the video information to reach each eye.
Another prior art approach also requiring the use of special glasses follows the principles employed in the 3-D movies of the early 1950's. Here, the glasses worn by the viewer are frequency filtered or color filtered and all of the information intended for one eye is encoded in one color and allowed to pass through the color filter for the given eye and likewise, all the information intended for the other eye is encoded in a different color and allowed to pass through the filter associated with that other eye. Use of this scheme naturally distorts the true colors of the image being presented on the face of the CRT.
Still another prior art approach which is somewhat more clumsy and expensive involves a special set of spectacles or glasses that have the LCD shutters individually attached for each eye and synchronized with the CRT such that the shutters associated with each eye open or blink every other frame. As a result, for one given frame, the right eye receives the image and then for a subsequent frame, the left eye receives it. This latter arrangement requires a cable or wireless linkage to the CRT to maintain synchronization between the frame switching occurring on the CRT and the shutter flipping taking place on the viewing lenses.
The Eichenlaub U.S. Pat. No. 4,829,365 describes in it various other related approaches for creating 3-D images to a viewer of a scene on a CRT and those interested in further information relating to such alternative arrangements are referred to that document